Chain saw



FIG. 1 is a perspective view of a chain saw showing our new design;

FIG. 2 is another perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a plan view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a right side view thereof; and,

FIG. 8 is a left side view thereof.

The broken lines shown in the drawings form no part of the claimed design. 

The ornamental design for a chain saw, as shown and described. 